Dental oral irrigating apparatus presently exist for generating and applying a stream of liquid to areas of a person's mouth. Some such apparatus are electrically powered and present potential danger to the user. Other such apparatus are powered and controlled by the liquid pressure from a water line. Examples of such latter units are disclosed in prior U.S. patents Nos. to Handler, et al., 5,218,956, to Gilbert, 3,500,824, to Drapen, et al., 3,225,759, to Chernack, 4,979,503. Such prior apparatus allow the user to selectively provide a discharge of only water or of water combined with a second liquid such as medication, mouthwash or the like. The apparatus disclosed by the above-noted patents all provide a reservoir for the secondary liquid mounted on the hand-holdable control and dispensing unit, which adds substantially to the size and weight of that unit. Further, because of the limited amount of secondary liquid that can be held in such a reservoir, the reservoir would have to be refilled frequently. These prior art apparatus also have various other limitations and deficiencies. Gilbert has no way to adjust the ratio of mix of the two liquids. In Handler the control of the flows of the primary and the additive liquids is controlled by two separately independently operable control levers so that the desired proportioning between the two liquids has to be reestablished each time the device is turned back on. In Drapen there are two separate controls on the handheld unit, one a depressible off/on switch, the other a rotatable element for controlling flow of the second liquid and which would appear to require the second hand of the user to operate. In Chernack there are two separate flow controls on the handheld unit. One an on/off for the second liquid and the other a water input flow control, with the amount or mixture of the second liquid being fixed with relation to the water flow.
Other water-powered oral irrigating devices disclosed secondary liquid reservoirs on the base, but lacked user control over the mixing ratio: See Harlem, et al., U.S. Pat. No. 5,004,158 and Thompson,